Currently, a basic mechanism of online charging is as follows. A charging trigger function (CTF) applies for reserving a quota of a rating group from an online charging system (OCS), the OCS grants a quota, and the CTF performs quota management, quota usage, and charging information collection, and when detecting that a charging reporting condition (trigger condition) is satisfied, reports collected charging information to the charging system.
In a 4G network, a policy and charging enforcement function (PCEF) at a gateway is a CTF. The PCEF determines a charging mode (online charging or offline charging), a statistics collection method (traffic, duration, or the like), a rating group (referred to as a charging key in this application), a reporting granularity, and the like according to a charging policy delivered by a policy and charging rules function (PCRF). A charging granularity includes service_identifier_level or rating_group_level. If the charging granularity is rating_group_level, the PCEF needs to report charging information for each rating group. If the charging granularity is service_identifier_level, the PCEF needs to report charging information for each rating group and each service identifier.
Drastic increase of data traffic poses new challenges to mobile networks. To deal with the challenges, an evolved mobile data network architecture that separates a control plane from a user plane appears. In the architecture, only control is performed on the control plane and deployment may be centralized; and a data flow passes through the user plane and deployment is distributed. A user may access a nearby user plane, to reduce a network transmission distance of data and a network delay and improve network efficiency.
Currently, the network architecture that separates a control plane from a user plane is already extended in a 4G network, and charging can be implemented to some extent in the network architecture that separates a control plane from a user plane. In the architecture, a ratio of a quantity of control planes to a quantity of user planes is 1:1. As shown in FIG. 1, a serving gateway-C, a PDN gateway-C, and a TDF-C are control planes, and a serving gateway-U, a PDN gateway-U, and a TDF-U are user planes. A control plane is a charging trigger point and performs a charging trigger function, and a user plane is a charging collection point and performs a charging collection function.
However, in a new-generation network architecture, to reduce a network delay and improve network efficiency in a movement process of a user, the user plane may be switched while the control plane remains unchanged. In addition, a user may simultaneously use a local service (for example, an operator service such as making a call or sending an SMS message) and an external service (for example, Internet access). To improve access efficiency, the user may be simultaneously connected to a plurality of user planes, where each user plane processes a different service scenario. In this case, a same rating group exists on different user planes. In a current online credit control mechanism, a quota granted by an OCS is distributed to different user planes for usage, but service quota usage on the different user planes greatly differs (for example, in a speed). This seriously affects quota management efficiency, costs, and accuracy.